A position encoder is a sensor for measuring physical quantities, such as length, angle and position, and is widely applied to the field of position measurement. At the current stage, most of the high-precision multi-degree of freedom displacement platforms use a plurality of linear gratings to be superimposed as a position feedback system. Such a position feedback system has significant disadvantages, wherein the perpendicularity and parallelism between platform degrees of freedom will affect the final position precision of a machine, which is called an Abbe error. Since a control system is not a closed-loop feedback, an error of a part caused by temperature or stress deformation also cannot be eliminated.
In order to solve the above-mentioned problems, many research and development departments and companies start to develop a planar encoder as a position feedback system. A planar encoder needs to use a planar grating for measurement. Such an encoder can achieve multi-degree of freedom position measurement, and furthermore can eliminate the Abbe error and realize the closed-loop control. A grating in a planar encoder is generally engraved with a two-dimensional periodic pattern, and the position resolution finally fed back by the grating can reach nanoscale. However, due to the complexity of a grating manufacturing process, the manufacturing cost of a large planar grating is very high, and particularly the machining process of the grating will be more complex when a high-precision position needs to be acquired.
Therefore, there is an urgent need for a novel position encoder in the art.